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  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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  <body>
    <script>
      const name = {};
      const age = {};
      const wmap = new WeakMap();
      wmap.set(name, "jack").set(age, 20);
      console.log(wmap.get(name));
      wmap.delete(age);
      console.log(wmap.has(age));
    </script>
  </body>
</html>
